As a cutting insert (hereinafter also referred to simply as “insert”) for use in a cutting process of workpieces, such as metals, there have been known inserts respectively described in Japanese Unexamined Patent Publication No. 2012-121131 (Patent Document 1) and Japanese Unexamined Patent Publication No. 2001-157903 (Patent Document 2). In the insert described in Patent Document 1, a cutting edge has a first region, a second region, and a third region. A rake angle of a rake surface in the third region serving as a flat cutting edge is larger than a rake angle of a rake surface in each of the first region and the second region.
In the insert (indexable insert) described in Patent Document 2, a cutting edge has a nose portion, a major cutting edge, and a flat cutting edge. A land is located along the cutting edge on an upper surface of the insert, and a land angle on the flat cutting edge is larger than a land angle on the nose portion.
The insert described in Patent Document 1 has no land surface for enhancing durability of the cutting edge, and the rake angle of the rake surface located inside the flat cutting edge is relatively large. Therefore, the flat cutting edge produces satisfactory cutting performance, whereas durability deterioration can occur. The insert described in Patent Document 2 has the land surface and the land angle on the flat cutting edge is larger than the land angle on the nose portion. Therefore, the durability of the flat cutting edge can deteriorate as in the case of the insert described in Patent Document 1.
The present embodiment has been accomplished in view of the above problem, and provides a cutting insert having a flat cutting edge with satisfactory cutting performance and durability.